A transparent substrate made of glass or polymer resin is used as a display of, for example, a personal computer, a slim television, a portable terminal or the like. When light is reflected at a surface of a display, a display content is difficult to be optically recognized, and therefore, it is desired for glass or a resin film constituting the surface of the display to improve contrast by preventing reflection from external light or stray light as less as possible. Further, it is also desired for other optical members such as a glass lens to prevent reflection at a surface thereof.
In order to prevent surface reflection of a display, a lens or the like, a method of carrying out coatings several times by vacuum deposition to reduce reflectance by differences in refractive indices thereof is generally adopted. However, according to this method, it is necessary to carry out the coatings several times for individual members, and therefore, not only is the method troublesome, but a problem of exfoliation of the coating is posed.
As another method of preventing reflection, a method of forming a minute structure at a surface of a substrate is known. Although as a method of forming such a minute structure, for example, there is known a method of patterning a surface of a substrate of quartz glass or the like by photolithography, an electron beam or the like, this procedure is complicated and it is difficult to form a minute structure at a surface having a large area.
Further, for example, a method of forming a minute acicular structure at a surface of a substrate by adhering small particles of Al or the like on an optical member of a quartz glass substrate or the like, and performing dry etching with a mask formed by the particles has been proposed (refer to Japanese Patent Application Laid-Open (JP-A) No. 2005-99707). However, according to this method, for respective substrates, a material that forms the mask is adhered as small particles by sputtering, thereafter, dry etching is carried out, and therefore, not only is productivity invariably low, but it is difficult to form an anti-reflection structure at a substrate having a large area.
As a method of forming an anti-reflection structure at a surface of an optical member having a large area, a method of forming an anti-reflection structure by producing a mold having a minute structure formed at a surface thereof and transferring the minute structure of the mold to an optical member is proposed. For example, a mold is produced by forming nuclei of Cr or the like in an island-like shape on a substrate such as a silicon wafer by vacuum deposition, thereafter, growing acicular crystals of silicon or the like on the nuclei by a CVD method or the like. Further, a method of forming an anti-reflection structure on an optical member of resin or glass by using the mold is proposed (refer to JP-A 2006-130841).
However, according to the above-described method, when the mold is produced, at least formation of the nuclei and growth of acicular crystals are needed, and therefore, the process becomes complicated. Further, although the produced mold can repeat molding for a member made of a resin, the mold cannot repeatedly be used for a member having a high melting point such as quartz glass or the like.
On the other hand, a method of forming a minute structure formed with columnar-shaped projections at a surface of a glassy carbon base member by ICP plasma and forming an anti-reflection structure onto another member by using it as a mold is proposed (refer to JP-A No. 2004-137105).
According to such a method, the minute structure can comparatively simply be formed, further, glassy carbon constituting the mold has a very high melting point, a mechanical strength thereof is comparatively high, and therefore, the minute structure can be transferred onto an objective member such as quartz glass or the like.
However, according to the above-described minute structure composed of the columnar projections, an anti-reflection effect is not sufficient and a minute structure having a higher anti-reflection effect is preferable.